Process of manufacturing propyl chloride



HJERPE ET AL 2,099,480

PROCESS OF MANUFACTURING PROFYL CHLORIDE CONVENTIONAL mzss'sures STILL PLANT File TAR CRACKED DISITILLATE LINE 5 ($51: 56.2.)

STRIPPED REFINERY Gas I COMPRES5ION ABSORPTION SYSTEM 7'0 #ABS 25mm 70 6A5 7/ SEPARATOE CUOLER omma ans .9 SEPARATOR COMPRESSION ABsoRPrw/v GASOLINE 75 i1- Elmo/rm 22' Eric Bhlt'l jerfie, MN: A illvam-iq. Grwse,

Nov. 16, 1937. E. B. HJERPE ET AL 9,

PROCESS OF MANUFACTURING PROIYL CHLORIDE Filed May 26, 1932 5 Sheets-Sheet 2 ammo/c4 I Mara-5e,

G/rtof w Nova 16, 1937 E. B. HJERPE ET AL PROCESS OF MANUFACTURING PROPYL CHLORIDE Filed May 26, 1952 5 Sheets-Sheet 3 Bo 25mm uzttlhu Patented Nov. 16, 1937 UNITED STATES PATENT OFFICE 2,099,400 raooass 0F MANUFACTURING mom cnmamn of Pennsylvania Application May 26, 1932, Serial No. 613,714

6 Claim.

This invention relates to utilization of petroleum refinery gas and apparatus therefor, and in its process phases it constitutes a continuous process wherein refinery gas containing methane,

ethylene, ethane, propylene, propane, butylene,

butane, and pentanes and higher boiling constituents is stripped of its contained gasoline vapor (pentanes and higher boiling components) and most of itsbutanes, for purposes hereinafter 10 described; wherein the residue is next stripped of methane for conversion into methyl chloride or otherwise usefully disposed of; wherein the residue from the last mentioned separation is further subjected to successive fractionation for isolation of cuts containing one olefin each (namely ethylene, propylene, and any residue of butylene) wherein the fraction containing ethylene is contacted with hydrogen chloride, or bromine or other reagents in the presence of a catalyst, for conversion of ethylene into ethyl chloride, ethylene dibromide, etc., and the product separately recovered from its diluent gas; wherein the fraction containing propylene is contacted with hydrogen chloride in the presence of a catalyst, for conversion of propylene into propyl chloride, and the propyl chloride separately recovered, or wherein the propylene is otherwise converted to useful chemical derivatives; and wherein the mixture of butanes and pentanes and higher boiling components first stripped from the refinery gas, or a light fraction thereof, is combined with the residual butylene fraction and the combined material is subjected I to high heat and pressure, with or without the presence of a catalyst, for polymerization into compounds boiling within the boiling point range of gasoline and suitablefor blending therewith. More specifically, in its process phases, this invention relates to a continuous process wherein uncondensed gas from the customary water cooled condensers of petroleum cracking stills and/or coke stills and/or steam stills (said gas comprising methane, ethylene, ethane, propylene,

, propane, butylene, butane, and higher boiling components) is subjected to compression and/or absorption steps to liquefy and thereby separate and remove butane and butylene and all higher boiling constituents, leaving a residue of stripped refinery gas; wherein this stripped refinery gas 59 is chilled to a temperature sufficient to liquefy all higher boiling components than methane and is introduced into a. tower and the methane fractionated out, the necessary chilling of the gas being eifected by expanding it through an ex- 55 pansion valve after compressing it to the necessary degree and cooling it with water; wherein the liquid residue from the last mentionedtower is expanded into a second tower and the ethylene and ethane similarly fractionated out for a purp se herein later described; wherein the liquid 5 residue of the last mentioned separation, now freed of ethylene, ethane and methane, is expanded into a fractionating tower and the propylene and propane fractionated out from residual butylene and butane, for the further sepa- 10 rate use of each of these fractions as hereinafter described; wherein the separated ethylene and ethane fraction is contacted with hydrogen chloride in the presence of a. catalyst such as aluminum chloride, to form ethyl chloride (the hyl6 drogen chloride being furnished in volume equal to or slightly less than that of the ethylene) and the ethyl chloride is stripped from accompanying diluent by being scrubbed with and absorbed in a petroleum absorbent oil, and the ethyl chloride 20 is finally'isolated by distillation from the absorbent oil; wherein the propane and propylene fraction hereinbefore described is contacted with hydrogen chloride in reacting proportio'n, in the presence of a catalyst such as stannic chloride, 25 to form propyl chloride; wherein the catalyst for the propylene-hydrogen chloride reaction is used in solution inpropyl chloride and the gases for the reaction are scrubbed with this mixture, and the propyl chloride produced by the reaction also 30 enters into solution in this same mixture; wherein the mixture of propyl chloride and catalyst is removed from the place of the reaction and. warmed to the extent necessary for vaporization of a part of the propyl chloride and the latter is 35 distilled therefrom andthereby separately obtained and the residue is returned to the presence of the reacting components for further use therewith; wherein the gas leaving the reaction chamber is scrubbed with a petroleum absorbent 40 oil and any absorbed propyl chloride vapor is distilled out of the absorbent oil and conducted to the point where the propyl chloride product is distilled off from the catalyst mixture; wherein the mixture of butane, butylene, and higherboil- 45 ing constituents separated out in the compression and/or absorption steps hereinbefore described, or a low boiling fraction of that mixture, together with residual butylene and butane from the propylene fractionation, is exposed to a temperature of the order of about 350 C. while being maintained under high pressure, to polymerize the so treated material'tohigher boiling point compounds and to reduce its tendency to form and deposit gum; and wherein the velocity of the ride may or may not be scrubbed with water for removal of any free hydrogen chloride and disposed of as commercialpropane; and wherein the tail gas from the before described polymerization of butylene, etc. may or may not be utilized as commercial butane.

One object of our invention is to economically produce useful commercial products from pctroleum refinery gas.

Another object of our invention is to convert petroleum refinery gas into products of maximum commercial value. Another object of our invention is to convert the ethylene content of the gas into ethyl chloride, and capture a maximum of the chloride so produced, while keeping the separatory processes to simplest possible form,

Another object of our invention is to convert the propylene content of the gas into propyl chloride, and capture a maximum of the chloride so produced, while keeping the separatory processes to simplest possible form.

Another object of our invention is to provide new and useful combinations of simple and cheap methods of obtention of intermediate products, with simple and cheap methods of conversion of those intermediate products into commercially valuable end products, with simple and cheap methods of capturing those end products.

The accompanying drawings illustrate the invention and bear such brief memoranda as will attain the advantages of a flow sheet.

Referring to the drawings, in Fig. 1 the numeral I indicates a stream of charging stock to a conventional cracking still comprising cracking coil 2, separating and dephlegmating tower 3,

condenser 4, and separator 5. These elements do not constitute a portion of this invention but are included for clarity of presentation. After condensation of cracked distillate in the condenser 4 the distillate is separated from accompanying uncondensed gas in separator 5. This gas, conducted away through line 6, is raw material used in the process which constitutes our invention. Other raw material for our process is the corresponding uncondensed gas from petroleum coking stills, lubricating stills, and steam stills. Any one of these gases along or any mixture of them is acceptable raw material and this raw material will hereinafter be referred to as still gas, or petroleum refinery gas.

The first step in the process which we have invented is to strip the gas of butylene, butane, pentanes and all high boiling constituents, at least a portion of which will be subjected to further steps as hereinafter described. This separation may be effected in various ways and we have found compression and absorption methods very satisfactory, with subsequent controlled fractionation of the absorbed material. Absorption is pression stage. This compression and subsequent cooling will liquefyv some of the higher boiling constituents of the gas and so a separator is placed in the line which conducts the cooled gas from one compression stage to another compressor. Liquefied material removed from this separator is termed compression gasoline and its subsequent treatment will be hereafter described. The drawing, lower part of Fig. 1, depicts two stage compression with compressors I and I0, followed by recooling in coolers 8 and II respectively, and removal of compression gasoline at separator 9, positioned immediately before the second compressor. The compression gasoline is conducted away from separator 9 through line l3. After compression to the desired degree, and subsequent recooling as described, the gas is introduced into an absorber I! where it flows counter- .current to and in open contact with a stream of absorbent oil introduced thereinto through line H. The absorbent oil absorbs most of the butane and practically allhigher boiling constituents of the gas, and the remainder of the gas, which we shall term stripped refinery gas, leaves the absorber "through line IS. The presence of plates in the absorber adds greatly to its effectiveness. The absorbent oil, rich with dissolved constituents of the gas, leaves the bottom of absorber l2 through line l6 and is introduced through line l8 into a tower l9 where the absorbed constituents of the gas are distilled 0i! and fractionated. Tower I9 is preferably operated under a superatmospheric pressure and should its pressure not be sufliciently below that of the absorber to cause the necessary flow through lines l6 and I8, a pump IT can be inserted in the line to effect the transfer of the liquid. Heat for distilling the absorbed constitufractionated vapors from tower 99 pass to, and

are condensed by, condenser 20. The eiiluent of the condenser passes to gas separator 2! where any unliquefied components of the gas are separated from the liquefied components. The condenser 20 and gas separator M are maintained under the same pressure and the pressure and temperature of the condenser are chosen to assure liquefaction of the highest possible proportion of the butane and butylene without liquefaction of propane or propylene. The butylene, butane, and higher boiling fractions of the refinery gas which are liquefied in; condenser 26 and separated from accompanying gas in separator 2| are conducted away through line 22. This line 22 joins line l3, previously described, and the combined stream passes through line A to another portion of the process. That portion of the petroleum refinery gas which passes through condenser 20 without being liquefied therein passes out of the top of gas separator 26 through line 23. This line joins line H, previously described, to form line B, and the combined stream in line B is termedstripped refinery gas. This stripped refinery gas contains some butylene and butane and all of the lower boiling constituents of the petroleum refinery gas. The relative proportions of the various constituents vary widely according to the kind of oil from which it originates, the kind of still in which it is produced, the temperature, pressure, and other conditions attending its creation, and the condensation of accompanying vapors in the still condenser (condenser 4 or its equivalent), One typical analysis of the stripped refinery gas-insofar as any analysis could be termed typicalwas the following, observed in operation of the process herein described and claimed.

Per cent Methane--- 45 Ethylene---" 5 Ethane 20 Propylene 8 Propane 15 Butylene--- 3 Butane 4 The stripped refinery gas is conducted by line B from that portion of the process depicted in Fig. 1 to that portion of the process which is depicted in Fig. 2, which will now be more fully degree is necessary to efiect that cooling at the expansion valve which is requisite for liquefaction at tower pressure of all constituents of the gas which boil at higher temperatures than methane. The tower pressure is advantageously chosen to permit further pressure drop in subsequent fractionating steps and yet maintain suitable working pressureat the last fractionating step. The methane is fractionated out in the first tower, 35, depicted in Fig. 2 and in our practice of the-invention we have found a pressure of 500 pounds per square inch above atmospheric,

before expansion, to be suitable for a gas such as the one of which an analysis is shown above, and a pressure of seven atmospheres within the tower to be quitesatisfact'ory. This pressure is generated by compressor 24 and the heat gen erated in compression is removed from the gas by a cooler 25. The compressed and recooled gas is then in condition for chilling by expansion, for introduction into the tower at 33 and for fractionation therein. Expansion and consequent cooling is efiected at expansion valve 3|. Maintaining a pressure of seven atmospheres within this tower we takeoff the 45 per cent methanecontent of the gas with a tower head temperature of minus 140 C. and the remainder of the gas leaves the base of the tower in liquid form at a temperature of minus 60 C. The fractionation in the tower is more easily controllable if we have a chilling means in the tower head and a warming means in the tower base. These are readily provided for by closed coils 21 and 32 in the tower base and head, respectively, and by-pass connections in the incoming gas line, to admit of circulating this gas therethrough in such quantity as is necessary to obtain the required control. Three valves 28 are shown for permitting the use of regulated amounts of the unexpanded gas for controlling the temperature of the tower base and similar by-pass connection and valves are provided to permit the use of regulated amounts of the expanded gas for controlling the temperature of the tower head, The by-pass connection and valves 28 having been illustrated in connection with coil 21, their similar arrangement in connection with head coil 32 has been omitted from the drawings for simplicity of illustration. These same remarks apply as to the head coils intowers 40 and 15, each of which is provided with by-pass connections similar to coil 21, but which connections have been omitted from the drawings for simplicity of illustration. Immediately before expanding the gas through expansion valve 3| we may pass it through a heat interchanger 30 wherein it is cooled by heat interchange with methane leaving tower 35 at very low temperature. The heat interchanger may be superimposed upon tower 35, as depicted in Fig. 2, and communicate therewith through .a pierced diaphragm 36. The methane finally flows away through line 31 for utilization.

The liquid residue leaves tower 35 through line 34 and comprises ethylene, ethane, propylene, propane, and some butylene and butane. This liquid is discharged into tower 40 at 42 for fractionation of ethylene and ethane from the propylene, propane, butylene, and butane. Tower 40 may be provided with coils 38 and 39 for assisting in controlling the head and base temperatures thereof, and these coils are connected with line 34 in by-pass arrangement and sequence as already fully described in connection with coils 21 and 32. A pressure of six atmospheres is ma.intained in tower 40 and the ethylene and ethane leave the top of the tower through line C at a temperature of minus 50 C., while the propylene, propane, butylene, and butane leave the base of the tower through line 43 at a temperature of minus 15C. The head temperature of tower M is controlled correctly when the gaseous emuent exhibits substantially no absorption with sulfuric acid while giving a substantial bromine absorption.

Fig. 3 illustrates the further utilization of the ethylene-ethane fraction from tower 40. Hydrogen chloride from a source M is conveyed through line E6 to join the ethylene-ethane mixture in line C and the combined stream continues on as line M. If the pressure of the hydrogen chloride at its source is insufilcient to force it through line Wits transfer may be efiected by a rotary compressor or equivalent means, or an ejector may be inserted in line C, at the junctiton with line 45, to induce adequate flow. The pressure of the gas in line C may be reduced prior to the junction of line 86 from hydrogen chloride source 44, or it may be reduced at a subsequent point, but in either case we reduce the pressure in the gas line prior to the catalyst chamber, so the pressure therein will be approximately atmosphere.

Hydrogen chloride is used in the proportion of 36.5 parts (or very slightly less) by weight to 28 parts of ethylene. This corresponds to one volume (or very slightlyless) of hydrogen chloride to one volume of ethylene. The mixture of ethylen'e, ethane, and hydrogen chloride from line 41 is then brought to the desired temperature and introduced into the presence of a catalyst, resulting in the prompt generation of ethyl chloride. Anhydrous aluminum chloride is an effective chlorination catalyst for this purpose and other chlorides have been found satisfactory. We find that our process can be practically and profitably conducted with gaseous mixtures inwhich the ethylene content of the ethylene-ethane mixture is even less than ten per cent although we prefer to not operate on gases much poorer in ethylene than ten per cent. The gas analysis already recorded is common and it will be noted that the ethylene content of the ethylene-ethane mixture in this particular gas is twenty per cent. The great dilution of the ethylene is one of the two factors which make the utilization of this fraction a diflicult problem, for it results in an extremely dilute ethyl chloride. which must then 5 be separately recovered.

Referring again to Fig. 3, the mixture of ethyl ene, ethane, and hydrogen chloride from line 41 is passed through a coil 48 situated in a heating chamber 49 and heated in its passage there through to a temperature of about 350 F. and it is then brought into the presence of catalyst in chamber 50, which latter is surrounded by a temperature maintaining device 5|. A contact of from one to two minutes with the catalyst is ordinarily ample when using reasonably fresh catalyst. A temperature of 350 F. should not be exceeded when using very fresh aluminum chloride because of its tendency to sublime, but with use it seems to gradually convert into( a double compound requiring higher temperature for its vaporization and we find that tempera-. tures of 400 F. are then practicable. After one or two minutes the ethylene will have been con verted to ethyl chloride and will exist as a vapor, in very dilute form, in mixture with .ethane and any excess hydrogen chloride. The vapors and gases are next conducted by line 52 to a cooler 53, wherein their temperature is reduced to ap-v proximately atmospheric temperature. If hydrogen chloride has been used in such quantity as to result in free hydrogen chloride beyond the catalyst chamber 50 it is next removed in appropriate manner.

We have found that petroleum oils are good absorbents of ethyl chloride but under our conditions, have no substantial absorbent action toward the accompanying products of our reaction, and we have solved the diflicult problem of recovering the ethyl chloride by the use of an absorption system wherein the gases are scrubbed with, and the ethyl chloride is absorbed in, a

/ petroleum absorbent oil which has no substantial volatility in relation to that of ethyl chloride; the absorbent oil after scrubbing the gases and-.absorbing the ethyl chloride is sent to a stripping still and fractionator for removal of the ethyl chloride content; and finally the undiluted vapors of ethyl chloride may be separately condensed if desired in liquid form. In Fig. 3 we have illustrated an absorption tower 59 and we' ordinarily operate this under a pressure of about fifty pounds above atmospheric. this pressure being secured by the aid of a compressor 55. The reaction products pass from cooler 53 to compressor 55 through line 54 and are discharged from the compressor through line 56. This lineconveys them to a recooler 51 where the heat resulting from their compression is removed prior to their introduction into absorption tower 59. The ethyl chloride vapors and accompanying gas are introduced into the bottom of the absorption tower, as shown, and absorbent oil is introduced at the top through line 61 and fed down, as shown, in counterfiow to the material being scrubbed. A series of plates in the absorber adds greatly to its effectiveness. After having had its ethyl chloride content removed by the absorbent oil, the tail gasethane--is discharged from the top of absorption tower 59 through line 60, and goes on for further utilization. Absorbent oil containing ethyl chloride is removed from the base of ab-v sorption tower 59 through line H and conveyed to the combined stripping still and fractionator 82 wherein it fluid through a closed coil 63 and the ethyl chloride content is distilled out. The ethyl chloride vapors pass from the top of tower 62 through line 64 to condenser 68, and ethyl chloride is separately discharged therefrom through line 69. The pressure generated in absorption tower 59 by means of compressor 55 is advantageously continued through to condenser 68 so that the ethyl chloride can be condensed with the aid of water at commonly obtainable temperature. A circulating pump withdraws stripped absorbent oil from the base of stripping still 62, through line 65, and dischargesit through a recooler 66 and line 61 back into the top of the absorption tower 59.

Figxiia is an alternative arrangement of elements 41 to 53 of Fig. 3, as indicated. The process of Fig. 3a is primarily the process of Fig. 3, but is altered somewhat to permit of better utilization of available heat, and reduction in the amount ofoutside cooling agent required. Instead of one heating coil 48 in heater 49, as shown in Fig. 3, the invention of Fig. 30. provides two coils 48a and 48b in two heaters 49a and 49b. The gases from line 41 are first heated'in coil 48s by the hot products of thereaction, conducted from catalyst chamber 50 to heater 49a through line 525- After being heated in coil 489. by the hot reaction products, the gas from coil 48a goes to coil 48], situated in heater 49s and is there raised to the requisite temperature by any effective heating means. After giving up some of their heat in heater 49a the hot reaction products pass through line 52b to cooler 53a and are there cooled the same as in cooler 53 of Fig. 3. Otherwise the process of Fig. 3a is the same as the process of Fig. 3.

Returning to Fig. 2, a mixture of propylene, propane, butylene, and butane is removed from the base of tower 40 through line 43 under a pressure of six atmospheres. This is conveyed through line 43 to tower l5, and is expanded at expansion valve ll prior to its introduction thereinto at 14. Tower is provided with base coil 12 and head coil 13 similar to coils 21 and 32 of tower 35 and completely described in that connection. The contents of line 43 or a portion of them may be by-passed through coil 12 for regulation of the temperature of the tower base, and all or a portion of them, after expansion through valve H, may be by-passed through coil 13 for regulation of the tower head temperature. As previously stated the by-pass connections for coil 13 have been omitted from the drawings for purpose of simplification. We operate tower 15 at a pressure of .five atmospheres and maintain therein a head temperature of 0 C. and a base temperature of plus 35 C. Thereby we effect fractionation of the incoming stream and take oii from the tower head, through line 16, a mixture of propylene and propane, and from the tower base we take ofi a residue of butylene and butane through line D. The butylene-butane fraction is conducted away through line D for further utilization.

We ordinarily use the propylene-propane fraction from tower 15 for manufacture of a propyl chloride, although our invention also comprehends its conversion into other useful chemical is heated by circulation of a hot- 44 is not sufllcient to cause its flow into line 16,

a centrifugal compressor 45 or equivalent means may be used to force it. The difficulties attendant upon handling HQ] in a compressor limit the pressure attainable at this point, and the pressure of the propylene-propane mixture in line 18 must be chosen to permit introduction of HCl at attainable pressure. A pressure of ten pounds above atmospheric in the reaction vessel is quite satisfactory and centrifugal type compressors can readily compress hydrogen chloride to that extent. We usually maintain a pressure of ten pounds above atmospheric in the reaction chamber. The combined streamof propylene, propane, and hydrogen chloride is conveyed through line 11 to the reaction chamber 18, where it comes in contact with a catalyst, and the reaction is accomplished. For catalyst in this reaction we prefer stannic chloride, but other chlorination catalysts, such as titanium tetrachloride, zirconium tetrachloride,,bismuth chlo-- ride, and others are useful for the purpose. We

prefer to use our catalyst dissolved or suspended in propyl chloride. We use the latter term to include either normal or isoepropyl chloride, or a mixture of these, while by chlorination catalyst" we mean a catalyst capable ofv catalyzing the reaction between hydrogen chloride and ethylene or propylene to form the respective chlorides. We always conduct the reaction at a temperature below the boiling point of the product (35 C. at atmospheric pressure in the case of iso-propyl chloride) and on down to C. The results are best in the neighborhood of the latter temperature. For reaction chamber 18 we use a vertical tower wherein the catalyst, dissolved in propyl chloride, flows counter to an ascending stream of gas from line 11. The presence of plates or some other form of packing in chamber 18 adds greatly to its effectiveness. The propylene and hydrogen chloride react in the presence of the catalyst and produce propyl chloride. Propane and other tail gases leave reaction chamber 18 through line 8| and the propyl chloride product goes into solution with the propyl chloride-catalyst mixture. Propyl chloride is recovered from fractionating tower 88 to which the propyl chloride and catalyst mixture is conducted through line 88 and heater 82. A pump 8i is inserted in line 88 if additional force is necessary to transfer the liquid from reaction chamber 18 to fractionating column 83. The heating in heater82 is regulated to distil ofi a quantity of propyl chloride approximately equal to that being currently produced, thereby leaving a liquid residue of propyl chloride and catalyst for return to and re-use in reaction chamber 18. In column 83 propyl chloride is removed as a. side-stream, propyl chloride-catalyst mixture is removed from the base of the tower through line 84, and anyuncondensed vapor, together with gas which may have been in solution in the incoming stream, is' taken off from the tower head through line 86. A coil or equivalent temperature controlling means I 3| may be provided in column 83, below the point where propyl chloride is taken oil, to prevent any catalyst being carried over. A similar temperature controlling element 81 in the tower head is useful in condensing out the propyl chloride. The propyl chloride-catalyst mixture is returned throughline 84, pump, 88, cooler 88,- and line 18 to the top of reaction chamber 18 for re-use therein.

It is cooled in cooler 88 to proper temperature for conduct of the reaction, as previously described. Any vapor and gas leaving the .top of tower 83 is conducted by line 86 and a blower or compressor 88 (if necessary) back to reaction chamber 18, where any contained propyl chloride will be captured. The return of lines 84 and 88 to reaction chamber 18 assures recapture at that point of any propyl chloride escaping from tower 83 through these lines, so tower 33 can be operated with consideration solely to the purity of the propyl chloride taken off through line 85. tower 83 can of course be constructed as two towers in series,'or as a simplified single tower,

according to the importance attached to purity of the recovered product and to the loss of propyl chloride in the tail gas. When constructed astwo separate towers heater 32 will discharge into the first tower, stream 84 will leave the base of the first tower, stream 85 will leave thebase of the second tower, and stream 86 will leave the top of the second tower. In the case of a simplified single tower catalyst mixture leaves the base and all other products go to a condenser and separator.

The tail gases, of the reaction chamber 13 have already been described as leaving through line 8I. They may discharge from the system at that point, or they may be subjected to an.-.

absorption step for recapture of contained propyl chloride, as illustrated in Fig. 2. Referring to Fig. 2 the tail gas leaving reaction chamber 13 through line 8I is recompressed by compressor 82 and forced into the bottom of an absorber 83 where it is scrubbed by a counterfiuent absorbent 98 in the base of stripping tower 81. Strippedabsorbent from the base of stripping tower 81 is conducted away from the base of the tower by line 89.to recirculating pump I88, which pump forces it through a cooler I8I and back through line 84 for re-use in absorber 83. The material stripped from the absorbent oil in stripping tower 81 is conducted away from the head of the tower through line I82 and conducted to tower 83. A compressor 'or a blower I83 is interposed in the line to step up the pressure if necessary.

Theoretically this process should produce normal propyl chloride and iso-propyl chloride, but in practicing the invention we get a very good yield of iso-propyl chloride and do not find the normal chloride in measurable quantity. Either the normal or iso-propyl chloride is a satisfactory carrier for the catalyst and we ordinarily use the product of our process for this purpose.

The description of that portion of our process which is illustrated by Fig. 1 described the withdrawal of gasoline from separator 8 through line I3, the withdrawal of gasoline from separator 2| 'through line 22 and the joining of these two 85 oil introduced at the top of the absorber through 6 describes the withdrawal of residual butane and butylene from tower 15 through line D.

The constitution of petroleum refinery gas will vary from time to time in a refinery and it will vary between different refineries according to the oil being operated upon and the specific conditions attending creation of the gas. Gases of different constitutions will have different thermodynamic properties and the cooling resulting from expansion of different gases will vary. Therefore the exact pressures and temperatures for fractionation and expansion stated herein may require alteration for specific gases. With the aid of standard tables of physical constants, the data herein given, and-the application of the well known gas laws, anyone skilled in the art here dealt with can readily compute the proper conditions for a specific gas. Obviously, external cooling can be supplied to assist fractionation if necessary.

Obtention of a fairly concentrated stream of ethylene in line C (Figs. 2 and 3) for manufacture of ethyl chloride may also be effected by an alternative process.which is a combination of fractionation and differential absorption steps. In a typical practice of this invention the gas operated upon was of the following analysis:

We found only three principal apparatus elements necessary, namely, a fractionator, an absorber, and a flash tower. Incidental apparatus elements included compressors, heat exchangers, drip traps, condensers, and coolers. In this alternative process the gas is compressed to a pressure of about 500 pounds per square inch and cooled to about F. Any condensate is removed from the gas stream and the gas is then introduced into the fractionator at a point about midway of its height. In the fractionator the gas is scrubbed with a stream of reflux which is introduced at the head of the tower, and all methane and ethylene, and some ethane, leave the head of the fractionator, while most of the ethane, and all of the higher boiling components, leave the base of the fractionator. The fractionator is operated under a pressure of about 500 pounds per square inch and the head temperature is about 25 F. and the base temperature about 100 F. The reflux material used is part of the final product of the flash tower (hereinafter described), the remainder of which is discharged into line C (Figs. 2 and 3): it averages about 15 per cent methane, '70 per cent ethylene and 15 per cent ethane. Reflux is used in the fractionating tower in the proportion of one pound of reflux to about four or five cubic feet of gas introduced, or thereabouts, and it is introduced at a temperature of about 15" F., which temperature explains the fact that the gases leave the top of the fractionator at a tempreature about seventy-five degrees lower than they enter. A source of heat is provided in the base of the fractionator to assist fractionation. The methane, ethylene, and ethane discharged from the top of the fractionator are next introduced into the base of an absorber, where they are scrubbed under a pressure of about 490 pounds per square inch and at a temperature of about 90 F. with a close out absorption naphtha. Ordinarily we use one gallon of absorption naphtha to five cubic feet of gas. Methane is discharged from the top of the absorber as tail gas, and we send the enriched absorbent oil from the base of the absorber to a flash tower for removal of the absorbed ethylene. The rich absorbent oil is then warmed from about 90, at which it leaves the absorber, to about at which latter temperature we introduce it into the flash tower. The flash tower is operated under a pressure of about two hundred pounds per square inch. A heating means is provided in the base of the flash tower to aid the distillation of ethylene from the absorbent, and a base temperature of about 225 F. has been quite satisfactory at the operating pressure, with the particular absorbent naphtha we have been using. From the top of the flash tower we discharge the desired ethylene-rich stream, which runs about '70 per cent ethylene, 15 per cent methane, and 15 per cent ethane. Part of this stream we use for reflux in the fractionator, as already described, and the remainder we discharge into line C (Fig. 2), prior to the Junetion of line 46 therewith. Other combinations of temperature and pressure can of course be used. 1 The liquid residue from the fractionator can be further processed as above to procure fractions containing propylene and butylene, separately, in high concentration.

Another mode of getting gas at line C (Fig. 2) prior to the junction of line 46 therewith, which will contain ethylene as the only olefin, comprises sequentially compressing the gas; cooling it with water; absorbing everything boiling higher than ethane, and as much of the ethane as possible; and then washing the unabsorbed gas with dilute sulfuric acid for removal of contained propylene.

Throughout the various fractionations and stripping steps in the process illustrated in Figs. 1, 2, and 3, we may improve the separation by discharging a portion of themore closely separated product of one tower back into the head of a previous tower, to constitute an open reflux stream therein.

Throughout the various steps of our process for utilizing petroleum refinery gas we can of course reduce the number of steps in fractionating out a cut containing any particular olefin when it does not disadvantageously affect the usefulness of adjacent fractions or where, under the particular circumstances, the adjacent fraction is not to be used. Likewise, where it does not affect the usefulness of adjacent fractions, we can fractionate to get the desired olefin as the principal content of a fraction, accompanied only by minimal quantities of the components having adjacent boiling points.

As a catalyst for production of propyl chloride from propylene, stannic chloride has the particular advantages that its use seems unaccompanied by tar-forming side reactions, and it is recovered unchanged.

In the appended claims we use the term petroleum refinery gas to mean a residual gas from a petroleum refinery, which gas is relatively lean in olefin content. Such a gas is that produced by coking stills, steam stills, lubricating stills, and typical cracking installations which involve the passage of a stream of oil through cracking coils. One typical gas of such nature is that of f I 2,009,480 which an analysis is tabulatedherein and which" has an olefin content of 16%. As before stated do not use the term petroleum refinery gas to mean gas rich in olefins which is wholly or predominantly the product of a vapor phase cracking process; such gases being ordinarily characterized by more than 30% ofoleflm'conte'nt, and obviously presenting a very different problem than the type of gases herein described.

What we claim is:-'-

1. The process of manufacturing a propyl chloride from petroleum refinery gas which comprises isolating a fraction containing the olefin propylene but not containing any other olefin in large amount, contacting the propylene containing fraction with hydrogen chloride in the presence of a catalyst consisting of stannic chloride, with consequent formation of propyl chloride; remov-v which results from the ride from propylene,

of a catalyst consisting ofstannic chloride.

ing the propyl chloride product and any dissolved catalyst out of the presence of any components of the gas which have not entered into the reaction; and distilling oil. propyl chloride.

2. A process according to claim 1 in which the stannic chloride catalyst is dissolved in propyl chloride.

3'. A process according to claim 1 in which the stannic chloride catalyst is dissolved in propyl chloride and wherein the gas being operated upon is scrubbed with the solution of stannic chloride "in propyl chloride. 4 4. A process according to claim 1 in which the stannic chloride catalyst is dissolved 'in propyl and wherein the reaction is conducted neighborhood of zero chloride; at a temperature in the degrees centisrade.

5. The process of manufacturing propyl chlopropylene and hydrogen chloride in the presence 6. The process of manufacturing propyl chloride from propylene, which comprises contacting propylene and hydrogen chloride in the presence of a catalystconsisting of s'tannic' chloride, said catalyst being dissolved in propyl chloride.

ERIC 3. HJE'RPE. wnmam' A. onusn.

which comprises contacting 

